The invention pertains to the field of motion damping devices used with submerged marine instrumentation for damping instrumentation movement and displacement due to wave and water motion.
In underwater transducer and hydrophone installations, such as in a sonobuoy system for detecting submarine sounds and the like, the provision of a substantially stable platform for the hydrophone is of prime importance in order to reduce extraneous noises and signals and permit the most accurate sound pressure wave input characteristics.
The purpose of sonobuoy suspension systems is to attenuate the vertical motion imparted by surface wave action to a hydrophone platform as motion of the hydrophone due to surface wave action will result in the generation of spurious low frequency signals. The attenuation system itself must not produce low frequency lateral motion oscillation such as those commonly found in objects suspended in ocean currents resulting from periodic shedding of vortices in the flowing fluid.
In a free floating sonobuoy system it is also important that a high drag concentration in the vicinity of the hydrophone platform be produced to reduce the relative velocity of the flow past the hydrophone to minimize the magnitude of any occurring flow noise as well as reducing the frequency of the noise associated with boundry layer transition on the hydrophone surfaces. Additionally, the magnitude and frequency of any unavoidable motion associated with vortex shedding is simultaneously reduced.
Improved transducer suspension systems have been achieved by the utilization of complaint members such as shown in the assignee's U.S. Pat. No. 3,377,615. Additionally, the utilization of specialized configurations in floating and buoy systems for stabilization purposes are known as shown in U.S. Pat. Nos. 3,191,202, 3,500,783, 3,510,892 and 3,543,228. However, a damper assembly for use with submerged hydrophone assemblies wherein a mass damper of an effective construction capable of being concisely stored has not been previously successfully achieved.